Sound film recording



Jan. 6, 19 42; w, KELLQGG 2,258,752

scum: FILM RECORDING, v

Filed Aug. 20, 1940 z'sheets-sneet -1.

Enventor Llagg Edward Wife (Ittomeg Patented Jan. 6, 1942 SOUND FILM RECORDING Edward W. Kellogg, Moorestown, N. J assignor to Radio Corporation of America, a corporation oi.

Delaware I 5 Claims.

This invention relates to an improved method of sound'film recording producing double density prints.

The production of a sound film record having one density around the sound wave images and a greater density over the background of-the sound track thereby preventing noises due to pin holes in the film or from dust spots on the negative was proposed in Dimmick Patent 2,165,787, issued July 11, 1939. This method was subsequently improved on by Dimmick in his Patent 2,199,621, issued May '7, 1940. The apparatus of both these patents produces records having a .certain density around the sound track image and a greater density in the background.

The present invention is an improvement on the apparatus and method of the said patents in that it provides a method whereby double density positive prints may be secured from practically any type of ordinary negative which has been made with ground noise reduction.

This is accomplished by dyeing the negative film with a light-sensitive dye such, for example,

as one of the diazo dyes which is bleachable by light. The negative film is then run through a' special printer and the area of dyed emulsion Application August 20, 1940, Serial No. 353,351

inspection of the accompanying drawings, in

which is limited in an appropriate manner so as to provide clear areas where the higher density is desired on the print, and so as to leave the dye in the areas where the lighter density is to be produced.

One object of the invention is to provide an improved method of producing a doubledensity negative. i

Another object of the invention is'to provide a method of printing a double density positive from a negative recorded in the conventional Figure 1 shows the type of positive print to be produced. 7

Figure 2 shows the negative adapted to the production of such a positive film.

Figure 3 showsa printer which-may be used in the performance of the method, and

Figure 4 shows a modification of the printer.

Referring first to the positive film shown in Figure 1, the sound wave image 20 is, printed as in the aforesaid Dimmick patents tov such a density as to most accurately reproduce the sound. If this density is too light, the proper volume range will not be reproduced and, if the density is too gr'eat, filling in of the bottoms of the wave images will occur with consequent distortion. The two densities represented by 20 and 2 I, however, are not the optimum density for the printing of the area of the sound track which contains no modulation such, for example, as the middle portion 22 and the marginal portions 23 at regions of no modulation. It is desirable to print these portions to a very high density, so that any dust spots or similar imperfections on the negative will be printed in by diffusion of the light in the positive emulsion. Likewise, these portions of high density in the positive are less likely to transmit light and cause noise due to scratches or similar imperfections, which may occur on the positive film. The areas 2| between the sound -wave images and the dark background should,

for best results, be as clear as possible and the light modulation in reproduction is accomplished by the difierence in transmission between the soundwave images 20 and the clear area 2|.

In order to proiiuce in a single printing operaing to the very dark portions 22 and 23 .of the hibit less graininess than double density film 1 produced by previous methods.

Another object of my invention is to provide a double density film, without any loss of clearness positive print. It must be extremely dense in the portions corresponding to theclear portions 2| of the positive, and it must have an intermediate density such as to produce the proper density in printing in the area corresponding to the sound wave images 20 of the print.

The Dimmick patents above referred to disbe entirely clear in both regions H and I2, rather than having two different densities in these regions as shown in Fig. 2.

A further drawback to the type of negative disclosed in the Dimmick patent, having three different densities of silver image, is that the sound waves are registered between a gray and a black area in the negative, and this has two faults, as compared with a variable area negative made according to standard methods, in which the wave outlines are a boundary between a clear and a moderately dark area. The first fault is that the graininess of the negative prints through onto the print in greater measure than in the case of a negative with a-clear area and one shade of dark gray, and the second fault with the double density negative is that the photographic resolving power of the film is less between a gray and practically black area, than between a clear and a gray area.

In making the double density negative shown in Figure 2, I make the usual sound negative with ground noise reduction which is here illustrated at In as being of the'doubly modulated type now; in commercial'use in RCA Photophone recording, and described and claimed in Baker Patent 2,199,606. It will be apparent to those skilled in the art that the negative need not be of the specific type shown but it may, if desired, be of the type shown in Underhill Patent No. 2,104,716, which is an inverted type of double sound track, or the type shown in Robinson Patent No. 1,854,159, or the type shown in McDowell Reissue Patent No. 21,389, the type here illustrated being chosen due to the fact that it is a type of sound track in general commercial use.

After the negative image it! has been made, I treat the entire film or the sound track area thereof with an appropriate light-sensitive dye,

- such, for example, as one of the light-sensitive diazo dyes. Inasmuch as the diazo dyes themselves and the manner of manipulating them are well'known, they are not described in detail herein. An example thereof is given in British Patent 7453 of 1890. The invention is not limited to the use of such dyes, but other equivalent materials may be used.

Afterthe film is treated with the dye, it is run through a special printer which bleaches the dye in the envelope areas 12 and I3. Such a printer requires a sound reproducer 3', 5', 6', 8, 20, 2| which will produce an envelope current and a shutter 23 which will obscure the sound track area and be controlled by the envelope current,

the exposure being made at the point 1 where r the shutter is located. Such an apparatus is shown in the sound reproducer appearing in the upper portion of Fig. 1 of my Patent 2,096,811. The only modification of the construction of the apparatus that would be necessary to use it as a printer in the present invention would be the omission of the photocell 8 and its attendant mechanism, and the substitution of a high intensity exposing lamp 30 for the exciter lamp 3. In using this apparatus for exposing a negative of the type shown in Fig. 2 of the'present application, 2, W-shaped shutter would be substituted, movable vertically, for the shutter 23. If the in vention were applied to 'a sound record of the type shown in the McDowell reissue patent referred to above, then a shutter of the type shown in Underhill Patent 2,104,716 would be used, and, for other forms of track, the shutter would be correspondingly modified. If a sound track such as shown in Robinson Patent 1,854,159 is to be light might be placed in the printer.

used, then the shutter of my Patent 2,096,811

may be left unchanged.

In the printer, the areas l2 and I3, or the corresponding areas of such other sound tracks as may be used, are exposed to a sufficiently intense light to destroy the color, and the image is then "treated'in the usual fashion to render it substantially permanent.

An alternative procedure is to provide a masking print for the sound track areas which will permit additional exposure of the areas l2 and 13, outside the envelope. Such a masking print may be made, for example, as described and claimed in Cook Patent 2,125,890. The masking print would be placed in contact with the treated negative and the negative then exposed to a sufficiently intense light as before described.

Thisprocedure leaves the negative as shown in Fig. 2 with the area ll colored by the diazo dye and the area l0 colored by both the dye and the silver image, producing a much greater density. When this negative is printed, it will, as above described, produce a positive print, such as shown in Fig. -1 with the area of one density, and the envelope areas 22 and 23 of a much greater density.

It will be apparent that since the silver images used in making my double density negative can be exactly the same as are found best in present variable area recording,- my negative will not be at any disadvantage on the score either of graininess or of resolution. The dye which I introduce is an entirely grainless light absorber, and

does not in any way impair the sharpness of the photographic boundary line that outlines the recorded waves.

If it .is desired to have a neutral tint image ll on the negative, a black or gray dye may be used.

However, in order to control the relative density of the two portions of the print, it is preferable to use a colored dye and to control the color of the printing light. might be used and an adjustable wedge 32 transmitting various proportions of blue and green If the Wedge is substantially withdrawn, the density of the portion 20 in the positive print and the portions 22 and 23 will be determined only by the sensitivity of the positive film to the green light. If, however, the blue wedge is inserted in the beam to a greater degree, so that the transmitted light becomes proportionately blue, this blue light will be transmitted to a much less extent by the green image than would be a white light, or a mixture of the green and blue, and the image on the positive film of the area 20 willbecome correspondingly lighter as compared with the density of the portions 22 and 23. This feature of the invention is not limited, of course, to the use of a green dye and a blue transmitting plate,

since any more or less complementary colorsmay be used provided, of course, that the positive film is sensitive to the color transmitted by the area H and also to the color transmitted by the wedge, but that the color transmitted by the area ll shall be only partly transmitted by the wedge, and shall absorb enough of the light to which the print film is sensitive, to materially affect the exposure of the latter.

Alternatively, two printing lights may be used,

. one of which may produce a white light, for

For example, a green dye the other light may be a color for which an area H is substantially opaque, thereby permitting having a sound wave envelope record .including the steps of making a negative sound record on film, treating the negative sound record film with a light sensitive dye, removing the dye in the areas outside the sound wave envelope only, and

making a positive print from said negative.

3. The method of making a sound record film having a sound wave envelope record including the steps of making a negative sound record on film of the sound waves only, treating the negative sound record with a light sensitive dye, and removing the dye in the areas not occupied by the sound wave envelope.

4. The method of making a double density positive sound record film including the steps of making a negative sound record on film, treating the negative sound record film with a light sensitive dye, exposing the film to remove the dye in the areas not occupied by the sound wave envelope, and making a positive print from said negative.

. EDWARD W. KELLOGG. 

